JP2014173478A - Fuel injection valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection valve that improves uniformity in a circumferential direction of a swirl flow.SOLUTION: A fuel injection valve includes: a swirl chamber 22a that has an inner peripheral wall formed so that curvature can be gradually increased toward a downstream side from an upstream side; a passage 21a for swirl, which has an inflow area in a valve stem direction and which introduces fuel into the swirl chamber 22a; and a fuel injection hole 23a that is opened in the swirl chamber 22a. The passage 21a for swirl is provided in an inclined manner on the side of the fuel injection hole 23a positioned on the downstream side of the swirl chamber 22a.

Description

  The present invention relates to a fuel injection valve used in an internal combustion engine, and relates to a fuel injection valve capable of improving atomization performance by injecting swirling fuel.

  As a conventional technique for promoting atomization of fuel injected from a plurality of fuel injection holes using a swirl flow, a fuel injection valve described in Patent Document 1 is known.

  In this fuel injection valve, between the valve seat member whose downstream end of the valve seat cooperating with the valve body opens at the front end surface and the injector plate joined to the front end surface of the valve seat member, The injector plate has a lateral passage communicating with the downstream end and a swirl chamber whose downstream end is opened in a tangential direction, and the fuel injection hole for injecting the swirled fuel in the swirl chamber The fuel injection hole is disposed with a predetermined distance offset from the center of the swirl chamber to the upstream end side of the lateral passage.

  With such a configuration, atomization of fuel from each fuel injection hole can be effectively promoted.

  A fuel injection valve described in Patent Document 2 includes a valve seat body having a stationary valve seat, a valve closing body that cooperates with the valve seat body and is axially possible along a valve longitudinal axis, A perforated disc disposed downstream of the seat, the perforated disc having at least one inflow region and at least one outflow opening, the upper side having at least one inflow region In which the functional seat has a different opening geometry from the lower functional plane with at least one outflow opening as viewed in cross section, the valve seat body being at least one inflow of the perforated disc The region is partly directly covered by the lower end surface, and at least two outflow openings are covered by the valve seat.

  With such a configuration, an S-shaped drift is realized in the flow for improving the atomization of the fuel, and a spray shape having high atomization quality is formed.

JP 2003-336562 A Special table 2000-508739

  In order to inject the swirl fuel whose swirl strength is substantially symmetrical (highly uniform in the circumferential direction) in the circumferential direction of the swirl from the fuel injection hole, the swirl flow is substantially symmetrical (circumferential direction at the outlet of the fuel injection hole). Therefore, it is necessary to devise a flow path shape including a swirl chamber (swirl chamber) shape and a lateral passage (swirl passage). In particular, since the total volume of the fuel flow path affects the accuracy of the injection characteristics (accuracy decreases as the volume increases), it is necessary to reduce the volume of the flow path as much as possible to improve the uniformity of the flow in the circumferential direction of the swirl chamber. is there.

  In the prior art described in Patent Document 1 and Patent Document 2, the fuel that has flowed in from the valve shaft direction reaches the swirl chamber via a lateral passage that extends in a perpendicular direction. In such a flow path configuration, the flow of fuel suddenly changes at the inlet of the lateral passage, and therefore induces a biased flow in the cross section of the flow path. If such a biased flow reaches the swirl chamber without being sufficiently rectified, there is a possibility that a steep flow into the fuel injection hole will occur and the general symmetry (high circumferential uniformity) of the swirl flow may be impaired. There is.

  This invention is made | formed in view of the situation which concerns, and it aims at providing the fuel injection valve which improved the uniformity in the circumferential direction of a swirl flow.

  In order to achieve the above object, a fuel injection valve according to the present invention has a valve body slidably provided, a valve seat surface on which the valve body sits when the valve is closed, and a fuel flow. A nozzle body having an opening on the downstream side, a turning passage communicating with the opening of the nozzle body, provided downstream on the fuel flow, and downstream of the fuel flow than the turning passage A swirl chamber that is formed on the side and has a cylindrical inner surface and that swirls fuel inside to impart a swirling force; a fuel injection hole that is formed in a cylindrical shape at the bottom of the swirl chamber and injects fuel to the outside; In the fuel injection valve having the above, the turning passage is inclined toward the fuel injection hole.

  Symmetry in the circumferential direction of the swirling flow of fuel is improved, fuel thinning is promoted, and atomization with good atomization is achieved.

It is the longitudinal cross-sectional view which showed the whole structure of the fuel injection valve which concerns on one of the Example of this invention with the cross section along a valve shaft center. It is a longitudinal cross-sectional view which shows the nozzle body vicinity in the fuel injection valve which concerns on one of the Examples of this invention. It is a top view of the orifice plate located in the lower end part of the nozzle body in the fuel injection valve which concerns on one of the Examples of this invention. It is a partial enlarged plan view for showing the inclined structure of the turning passage in the fuel injection valve according to one of the embodiments of the present invention. It is sectional drawing of the BD direction of FIG. It is sectional drawing of the C direction of FIG. It is a partial expanded plan view for demonstrating the flow for the turning in the conventional orifice plate, and the flow in a turning chamber. It is sectional drawing of the F direction of FIG. It is sectional drawing of the E direction of FIG. It is sectional drawing of the G direction of FIG. It is sectional drawing of the G direction of FIG. It is a partial enlarged plan view for showing the projection part provided in the bottom face part of the passage for rotation in the fuel injection valve concerning one of the examples of the present invention. It is sectional drawing of the B direction of FIG. It is a partial enlarged plan view for demonstrating the flow for a turning in the orifice plate, and the flow in a turning chamber. It is sectional drawing of the G direction of FIG.

  An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a longitudinal sectional view showing the overall configuration of a fuel injection valve 1 according to one of the embodiments of the present invention in a section along the valve axis.

  In FIG. 1, a fuel injection valve 1 has a structure in which a nozzle body 2 and a valve body 6 are accommodated in a thin stainless steel pipe 13 and the valve body 6 is reciprocated (open / closed) by an electromagnetic coil 11 disposed outside. is there. Details of the structure will be described below.

  A magnetic yoke 10 surrounding the electromagnetic coil 11, a core 7 positioned at the center of the electromagnetic coil 11 and having one end magnetically in contact with the yoke 10, a valve body 6 that lifts a predetermined amount, and a contact with the valve body 6. A fuel injection chamber 4 that allows passage of fuel flowing through the clearance between the valve seat surface 3, the valve body 6 and the valve seat surface 3, and a plurality of fuel injection holes 23 a, 23 b, 23 c, downstream of the fuel injection chamber 4, An orifice plate 20 having 23d (see FIGS. 2 to 4) is provided.

  A spring 8 is provided at the center of the core 7 as an elastic member that presses the valve body 6 against the valve seat surface 3. The elastic force of the spring 8 is adjusted by the pushing amount of the spring adjuster 9 in the direction of the valve seat surface 3.

  When the coil 11 is not energized, the valve body 6 and the valve seat surface 3 are in close contact with each other. In this state, since the fuel passage is closed, the fuel stays inside the fuel injection valve 1 and fuel injection from each of the plurality of fuel injection holes 23a, 23b, 23c, and 23d is not performed.

  On the other hand, when the coil 11 is energized, it moves until it contacts the lower end surface of the core 7 facing the valve element 6 by electromagnetic force.

  In this opened state, a gap is formed between the valve body 6 and the valve seat surface 3, so that the fuel passage is opened and fuel is injected from the fuel injection holes 23a, 23b, 23c, and 23d.

  The fuel injection valve 1 is provided with a fuel passage 12 having a filter 14 at the inlet. The fuel passage 12 includes a through-hole portion that penetrates the center of the core 7 and is pressurized by a fuel pump (not shown). This is a passage that guides the fuel to the fuel injection holes 23a, 23b, 23c, and 23d through the inside of the fuel injection valve 1. The outer portion of the fuel injection valve 1 is covered with a resin mold 15 and electrically insulated.

  As described above, the operation of the fuel injection valve 1 controls the amount of fuel supplied by switching the position of the valve body 6 between the valve open state and the valve closed state in accordance with energization (injection pulse) to the coil 11. doing. In controlling the fuel supply amount, a valve body design that does not leak fuel when the valve is closed is employed.

  In this type of fuel injection valve, a ball (JIS ball ball bearing steel ball) having a high roundness and a mirror finish is used for the valve body 6, which is beneficial for improving the sheet performance. On the other hand, the valve seat angle of the valve seat surface 3 with which the ball is in close contact is an optimum angle of 80 ° to 100 ° with good grindability and high roundness, and the sheet property with the above-mentioned ball is extremely high. It can be maintained. In addition, the hardness of the nozzle body 2 having the valve seat surface 3 is increased by quenching, and unnecessary magnetism is removed by demagnetization treatment. Such a configuration of the valve body 6 enables the injection amount control without fuel leakage. Therefore, it is set as the valve body structure excellent in cost performance.

  FIG. 2 is a longitudinal sectional view showing the vicinity of the nozzle body 2 in the fuel injection valve 1 according to one embodiment of the present invention. As shown in FIG. 2, the orifice plate 20 has an upper surface 20 a that is in contact with the lower surface 2 a of the nozzle body 2, and the outer periphery of this contact portion is laser-welded and fixed to the nozzle body 2. The cross section of the orifice plate 20 is a cross section in the A direction of FIG.

  In this embodiment, the vertical direction is based on FIG. 1, and the fuel passage 12 side is the upper side and the fuel injection holes 23a, 23b, 23c, and 23d are the lower side in the valve axial direction of the fuel injection valve 1, respectively. .

  A fuel introduction hole 5 having a diameter smaller than the diameter φS of the seat portion 3 a of the valve seat surface 3 is provided at the lower end portion of the nozzle body 2. The valve seat surface 3 has a conical shape, and a fuel introduction hole 5 is formed at the center of the downstream end thereof.

  The valve seat surface 3 and the fuel introduction hole 5 are formed so that the center line of the valve seat surface 3 and the center line of the fuel introduction hole 5 coincide with the valve shaft core Y. Due to the fuel introduction hole 5, an inflow opening 20 b communicating with the fuel passage is formed on the contact surface between the lower end surface 2 a of the nozzle body 2 and the upper surface 20 a of the orifice plate 20 corresponding to the fuel passage located downstream.

  Next, the configuration of the orifice plate 20 will be described with reference to FIG. FIG. 3 is a plan view of the orifice plate 20 located at the lower end of the nozzle body 2 in the fuel injection valve 1 according to the present invention.

  Four swirl passages 21a, 21b, 21c, and 21d that are arranged at equal intervals (intervals of 90 degrees) in the circumferential direction from a position spaced apart from the center of the orifice plate 20 and extend radially toward the outer circumferential side in the radial direction are provided. Is formed. These turning passages 21 a, 21 b, 21 c, and 21 d form a concave fuel passage provided on the upper surface 20 a side of the orifice plate 20.

  The downstream end of the turning passage 21a is connected to communicate with the turning chamber 22a, the downstream end of the turning passage 21b is connected to communicate with the turning chamber 22b, and the downstream end of the turning passage 21c is connected to the turning chamber 22c. The downstream end of the turning passage 21d is connected to communicate with the turning chamber 22d.

  The turning passages 21a, 21b, 21c, and 21d are fuel passages that supply fuel to the turning chambers 22a, 22b, 22c, and 22d, respectively. In this sense, the turning passages 21a, 21b, 21c, and 21d are turned into the turning fuel supply passage 21a. , 21b, 21c, 21d.

  The wall surfaces of the swirl chambers 22a, 22b, 22c, and 22d are formed so that the curvature gradually increases from the upstream side toward the downstream side (so that the radius of curvature gradually decreases). At this time, the curvature may be continuously increased, or may be gradually increased from the upstream side toward the downstream side while keeping the curvature constant within a predetermined range.

  Typical examples of the curve in which the curvature continuously increases from the upstream side toward the downstream side include an involute curve (shape) or a spiral curve (shape) and a curve based on the design method of the centrifugal fan. In the present embodiment, the spiral curve is described, but the description can be similarly made even if the above curve is adopted assuming that the curvature gradually increases from the upstream side toward the downstream side.

  Next, the relationship between the turning passage 21a and the forming method of the turning chamber 22a and the fuel injection hole 23a according to one embodiment of the present invention will be described with reference to FIGS.

  FIG. 4 is an enlarged plan view showing the relationship between the swirling passage 21a having the inclined structure, the swirling chamber 22a, and the fuel injection hole 23a. FIG. 5 is a cross-sectional view in the B direction of FIG. 4 and is a view for explaining the flow of the turning passage 21a. FIG. 6 is a cross-sectional view in the C direction of FIG. 4 and is a view for explaining the flow of the turning passage 21a and the turning chamber 22a. One swirl passage 21a has a desired angle θ in the tangential direction of the swirl chamber 22a, and is open for communication. A fuel injection hole 23a is opened at the center of the swirl chamber 22a. .

  As described above, in this embodiment, the inner peripheral wall of the swirl chamber 22a is formed so as to draw a spiral curve on a plane (cross section) perpendicular to the valve shaft center line, and the swirl chamber 22a composed of the spiral curve is formed. In doing so, the characteristic configuration is briefly described below.

  The extension line (tangent) of the inner wall surface of the swirl chamber 22a and the extension line of one side wall surface 21as of the swirl passage 21a are designed not to intersect on the swirl chamber 22a side. A thickness forming portion 24a is provided between the end of the inner wall surface of the swirl chamber 22a and the side wall surface 21as of the swirl passage 21a. The thickness forming portion 24a is a thickness portion necessary for processing.

The starting point of the helical curve (which can be said to be the end point in this embodiment) coincides with the center of the fuel injection hole 23a. Here, the vortex center of the flow along the spiral wall surface coincides with the center of the fuel injection hole 23a.
Further, referring to FIG. 4, the inner peripheral wall of the swirl chamber 22a is designed by the equal differential spiral equations (1) and (2). The center o of the reference circle X when drawing the equal helix, the center o when forming the swirl chamber 22a, and the center o of the fuel injection hole 23a are located.
(Formula 1)
R = T / 2 × (1-a × θ)
(Formula 2)
a = Wk / (T / 2) / (2π)
Here, R is the distance from the center o when the swirl chamber 22a is formed to the inner peripheral wall of the swirl chamber, T is the diameter of the reference circle X when drawing the equidistant spiral, and Wk is swirled with the end point E of the swirl chamber 22a. This is the distance of the starting point S of the chamber 22a.

  The swirling passage 21a has a rectangular cross section for allowing the passage of fuel. Although not shown, the reference circular diameter, which is a reference for the diameter of the fuel injection hole 23a and the size of the swirling chamber 22a, is experimentally determined in advance. Select a value close to the required specification from the various data obtained. That is, it is selected according to the flow rate and spray angle required for the fuel injection valve.

Hereinafter, the configuration and operation of the inclined structure according to the present embodiment will be described.
First, the flow in the passage without the inclination of the turning passage 21a will be schematically described with reference to FIGS. 7 to 9 based on the analysis result of the inventors.

  FIG. 7 is a partially enlarged view for explaining the flow of the turning passage 21a and the turning chamber 22a in the orifice plate 20. As shown in FIG. FIG. 8 is a cross-sectional view in the F direction of FIG. 7 and is a view for explaining a characteristic portion of the flow in the length direction of the turning passage 21a. FIG. 9 is a cross-sectional view in the direction E of FIG. 7, and is a view for explaining the characteristic portion of the flow in the height direction of the turning passage 21a and the turning chamber 22a.

  In the flow in the width direction of the turning passage 21a, the fuel easily flows into the fuel injection hole 23a on the inlet side of the turning chamber 22a, and a flow 31b having a higher speed than the 21at side is formed on the side wall 21as side of the turning passage 21a. Is done. On the other hand, a flow 31c having a lower speed than the side wall 21as side is formed on the side wall 21at side.

  These flows 31b and 31c are generated because the flow 31a in the valve axis direction flows from the inflow opening 20b and then collides with the bottom surface 21ab of the turning passage 21a and is bent in a right angle direction. The inflow opening 20 b is a substantially semicircular opening formed between the opening of the fuel introduction hole 5 and the orifice plate 20.

  As shown in FIG. 8, the flow 31a colliding with the bottom surface 21ab of the turning passage 21a becomes a flow 31e with reduced speed while proceeding in the longitudinal direction, but the flow toward the height direction of the turning chamber 22a is weak enough. The turning effect cannot be obtained. In addition, the flow 31f directed to the lower side of the turning passage 21a is induced by the flow 31e, and as a result, forms a dead water area 31i. As shown in FIG. 9, the flow at the inlet of the swirl chamber 22a flows along the bottom surface 21ab of the swirl passage 21a and flows into the thickness portion 24a side of the swirl chamber 22a. For this reason, it strongly interferes with the flow 31d (see FIG. 7) on the fuel injection hole 23a side. Due to the influence of the interference, a flow 31h with a large velocity is formed at the inlet of the fuel injection hole 23a, thereby inhibiting flow symmetry (uniform swirl flow). Therefore, as shown in FIG. 10, the spray from the fuel injection hole 23a is asymmetric.

  The inclined structure of the turning passage 21a according to one embodiment of the present invention suppresses such a steep flow and rectifies the flow at the inlet of the turning chamber 22a in the height direction. Referring back to FIG. 4 to FIG. 6, the inclined structure of the turning passage 21a and the flow associated therewith will be described.

The turning passage 21a is inclined toward the fuel injection hole 23a by a desired angle θ with respect to the inlet portion of the turning chamber 22a. In other words, the center line DD of the turning passage 21a is inclined by θ with respect to the line segment BB perpendicular to the line segment CC passing through the center of the fuel injection hole 23a. The inclination angle θ is preferably 10 ° to 30 °. The flow 30a flowing in from the valve shaft direction collides with the bottom surface 21ab of the turning passage 21a, and then forms flows 30b and 30c toward the inner peripheral wall surface in the vicinity of the inlet of the turning chamber 22a. Since the fuel flow 30b is closer to the fuel injection hole 23a, the flow velocity is faster than 30c. Since the flow 30b having a high flow velocity can avoid interference with the flow 30d swirled (circulated) in the swirl chamber 22a, sufficient swirl is imparted. Further, as shown in FIG. 5, the flow 30e is rectified in the height direction when it goes to the entrance side of the swirl chamber 22a, so the wide dead water area 31i of FIG. On the other hand, as shown in FIG. 6, the flow velocity is restored at the height of the swirl chamber 22a, and sufficient swirl is imparted in the swirl chamber 22a to reach the fuel injection hole 23a. Therefore, the symmetry of the swirl flow can be improved at the outlet of the fuel injection hole 23a.
As shown in FIG. 12, the protrusion 25a is provided in the entire region in the width W direction of the turning passage 21a. Further, the length b in the longitudinal direction is set to 1/3 or less of the length L of the turning passage 21a.

On the other hand, as shown in FIG. 13, in the height H direction of the turning passage 21a, the height h of the protrusion 25a is set to 1/6 or less. Further, the protrusion 25a is formed so as to be located on the downstream side of the turning passage 21a (the inlet side of the turning chamber 22a).
With this configuration, the fuel flowing in from the inflow opening 20a flows from the bottom surface 21ab of the swirl passage 21a toward the upper surface of the swirl chamber 22a as shown in FIGS. 14 and 15, and in the height direction of the swirl chamber 22a. Since the current is rectified (41a, 41b), sufficient swirl is imparted in the swirl chamber 22a to reach the fuel injection hole 23a. Accordingly, the swirl flow can be made symmetric at the outlet of the fuel injection hole 23a. Therefore, as shown in FIG. 11, the symmetry of the spray from the fuel injection hole 23a is improved.

  Although the nozzle body 2 and the orifice plate 20 are not shown in the drawing, they are configured so that the positioning of both is simple and easy using a jig or the like, and the dimensional accuracy at the time of combination is improved. Yes. Further, the orifice plate 20 is manufactured by press molding (plastic processing) advantageous for mass productivity. In addition to this method, a method with high processing accuracy that is relatively free of stress such as electric discharge machining, electroforming, and etching may be considered. In such a configuration, not only the cost reduction effect is achieved, but also the dimensional variation is suppressed by improving the workability, so that the robustness of the spray shape and the injection amount is remarkably improved.

As described above, the fuel injection valve according to the embodiment of the present invention can suppress the influence of interference between the swirled fuel and the fuel from the swirl passage by inclining the swirl passage with respect to the swirl chamber. The flow is rectified in the cross section (width direction, height direction) of the turning passage. In particular, since a sufficient velocity distribution is maintained in the height direction at the entrance of the swirl chamber and the swirl chamber is supplied to the swirl chamber, the swirl chamber is guided to the inner wall surface of the swirl chamber and has a sufficient swirl. In addition, a uniform swirl flow is formed at the inlet portion of the fuel injection hole arranged at the vortex center of the swirl flow, and the thinning of the fuel is promoted.
Furthermore, since the thickness forming portion is provided, the collision between the fuel flow in the swirl passage and the fuel flow in the swirl chamber is alleviated, and a more uniform swirl flow is formed, facilitating fuel thinning.

  The fuel spray that has been uniformly thinned in this way actively exchanges energy with the surrounding air, so that the splitting is promoted immediately after the injection and the atomization is good.

DESCRIPTION OF SYMBOLS 1 Fuel injection valve 2 Nozzle body 3 Valve seat surface 4 Fuel injection chamber 5 Fuel introduction hole 10 Yoke 11 Coil 20 Orifice plate 21a, 21b, 21c, 21d Turning passage 22a, 22b, 22c, 22d Swirling chamber 23a, 23b, 23c , 23d Fuel injection holes 24a, 24b, 24c, 24d Thickness forming portion 25a Protruding portion

Claims (3)

A valve body provided in a slidable manner, a valve seat surface on which the valve body sits when the valve is closed, a nozzle body having an opening on the downstream side with respect to the flow of fuel, and the nozzle body A swirl passage that communicates with the opening and is provided on the downstream side with respect to the fuel flow; and is formed on the downstream side with respect to the fuel flow with respect to the swirl passage, and has a cylindrical inner surface; In a fuel injection valve comprising: a swirling chamber that swirls fuel inside to apply a swirling force; and a fuel injection hole that is formed in a cylindrical shape at the bottom of the swirling chamber and injects fuel to the outside.
A fuel injection valve characterized in that the turning passage is inclined toward the fuel injection hole. The fuel injection valve according to claim 1, wherein
A fuel injection valve, wherein a thickness forming portion is provided between the swirl chamber and the swirl passage. The fuel injection valve according to claim 1, wherein
A fuel injection valve characterized in that a protrusion is provided in the turning passage.